Cruz, a 3-year-old Samoyed who competing in his first Westminster this year, died Feb. 16 while competing in another dog show in Colorado -- just four days after the Westminster competition ended. Both the dog's co-owner, Lynette Blue, and his handler, Robert Chaffin, suspect the dog was poisoned.

"We have gone through all the steps of where he was, what was done, and he was always on a leash," Blue, 67, who has co-owned Cruz since birth and has raised and shown the fluffy, snow-white breed of dogs since the 1960s, told ABC News today. "He was never outside. He was always with the handler."

Cruz, short for his show name, GCH CH Polar Mist Cruz'N T'Party At Zamosky D, was competing at the 18th Annual Rocky Mountain Cluster Dog Show in Denver when he became sick, vomiting blood. Chaffin, his handler of over one year, who was also at the Westminster, took him to an emergency veterinary clinic, where he later died of internal hemorrhaging. The dog was cremated and a necropsy was not performed.

"We can't figure out a timeline where it could have happened while he was in the room or being walked," said Blue, who said she had no insurance policy on Cruz.

But according to Dr. Tony Johnson, a clinical assistant professor of emergency medicine at Purdue University College of Veterinary Medicine, Cruz's symptoms of internal bleeding and eventual death could also be attributed to natural causes such as cancer.

"Two of the things that will cause bleeding in the abdomen are cancer and rat poisoning and people often attribute it to poisoning as opposed to cancer," he said. "We see a lot of dogs that have bleeding in their abdomen due to cancer so that is a possibility."

Johnson added that it is "not an uncommon scenario" for an animal to not have an autopsy done, "but in the absence of a toxicology or pathology report," as in Cruz's case, "it becomes speculation," he said.

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(Photo Courtesy: Lynette Blue)

Blue said the only time Cruz was not being watched by Chaffin while in New York was when the dog was "benched" at Westminster, a time when the dogs are required to stay in an assigned area with other owners and breeders.

Cruz's handler, Chaffin, whom Blue says she "absolutely" does not suspect was involved in Cruz's death, is convinced that the dog was poisoned and said there was a four-hour window during which the dog could have been poisoned, but not by a competitor. Instead, Chaffin said he is suspicious of an animal rights activist he encountered at the dog show who "was just scowling at me and telling me how cruel I was."

"All of our competitors in the breed are good people," Chaffin told ABC News. "I don't think it was someone in the dog world. There are lots of crazy people out there."

A representative for People for the Ethical Treatment of Animals, which has sent people to Westminster in past years, brushed aside Chaffin's suspicion that an "animal rights activist" could have been responsible for Cruz's death.

"The accusation is ludicrous and he hasn't even identified the person as an animal rights activist," Lisa Lange, senior vice president at PETA told ABC News. "It was someone at the dog show who criticized him."

Lange said, in a statement to ABC News, that PETA protested at Westminster, in part, against what it sees as the glamorization of pure-bred animals.

"(M)ore than 7 million cats and dogs are entering U.S. shelters every year with half of them being euthanized due to a lack of good homes – homes that are filled with dogs from breeders and puppy mills because of Westminster. There's no excuse for breeding more dogs while homeless mutts (and purebreds) are literally dying for homes."

Blue said the show provides dog owners the option to hire security guards during their stay in New York, a sign that "it could be a dangerous situation." The owner was more open, however, to the possibility of other motivations.

"It could be some crazies or some animal rights fanatics," she said. "Or it's always possible -- he was a top-winning dog, so it's always possible, those things have happened -- that other people in the dog show world try to knock out top competition. ... You just don't know."

Chaffin criticized the Westminster Dog Show for lack of security.

"If I could do it all over again, I wouldn't go to Westminster," he said. "I won't go to that show again. It's not safe for dogs."

Westminster, in a statement issued to ABC News today, said, "We have never, to our knowledge, had an incident at our show where a dog has become ill or was harmed as a result of being poisoned.

"We are ultra cautious to the point where we do not allow dogs to be off lead at any time while at our show," the statement read. "Unfortunately, no autopsy was performed, so there are a lot of unanswered questions. No other animal which attended our show was reported to our show veterinarians with any incident of serious illness. We have been made aware that no rodent poison is used at the Piers and pest control is maintained through trapping."

Cruz, who did not place at Westminster, held the designation of "Grand Champion," a title given to dogs earning a total of 25 points with three major wins at other shows. Cruz had competed in at least 30 other dog shows over the past year, according to Blue.

After Cruz's death, the owner of a fellow competitive dog, not in Cruz's breed, came forward to offer a $2,000 reward for "any information that could lead to the arrest of the person who might of done this to Cruz," calling the possible poisoning a "worst nightmare."

Blue said she filed a complaint with the New York Police Department last week but is still awaiting a follow up call from the agency. A representative for the NYPD told ABC News it can find no record of a complaint filed by Blue.

"People just need to know they need to be aware of where their dogs are," said Blue. "This thing has just left a hole in my heart. It has taken some of the joy and fun out of showing and raising dogs. It's something I'll never get over."